1. Field of the Invention
This invention relates to an optical disc such as a CD-ROM (a Compact Disc read-only memory) which is designed to prevent illegally copying of information (for example, information of a television game or a computer game) recorded thereon. Further, this invention relates to a device for checking an optical disc to determine whether or not the optical disc contains illegal copy information. Moreover, this invention relates to a device for recording information on such an optical disc.
2. Description of the Prior Art
A CD-ROM or the like is manufactured according to the published standards such as ISO 9660 standards established by International Standard Organization. To prevent illegally copying of information from a legitimate optical disc in conformity with the standards, a copy protection code is preliminarily recorded on the optical disc. Thus, an optical disc containing such a copy protection code is judged to be legitimate. On the other hand, an optical disc lacking a copy protection code is judged to be illegal.
The effect of such a copy protection method is limited for the following reason. When all information on a legitimate optical disc is copied and transferred to another optical disc (a second optical disc), the second optical disc can also be used as a legitimate optical disc.
A Mini-Disc (MD) uses another copy protection technique called a serial copy management system (SCMS). The SCMS employs a copy protection code related to the permissibility of copying data. To prevent data recorded on an MD from being digitally copied twice or more, the SCMS refers to the copy protection code. Specifically, the copy protection code is preliminary written in a TOC (total-of-contents) area of the MD.
According to the SCMS, if the copy protection code in a first MD indicates the absence of a requirement for protection, copying data or information from the first MD to a second MD is permitted. During the copying process, the copy protection code indicating the presence of a requirement for protection is written into a TOC area of the second MD. On the other hand, if the copy protection code in a first MD indicates the presence of a requirement for protection, copying data or information from the first MD to a second MD is inhibited.
The effect of the copy protection method based on the SCMS is limited for the following reason. When all information on a legitimate MD is copied and transferred to another MD (a second MD), the second MD can also be used as a legitimate MD.